Method of making gravel filter pipes



Sept. 16, 1969 J. BoLEwsKl METHOD 0F MAKING @RAVEL FILTER PIPES Filad Nov. 21, 1966 INVENTOR Josef Bolewski ATTORN United States Patent O 3,467,740 METHOD F MAKING GRAVEL FILTER PIPES Josef Bolewski, 5 Georghausserstrasse, 6101 Zeilhard, Darmstadt, Germany Filed Nov. 21, 1966, Ser. No. 595,770 Int. Cl. B28b 7/32 U.S. Cl. 264-69 4 `Claims ABSTRACT 0F THE DISCLOSURE Gravel iilter pipes are made by placing an inflatable body within a perforated support body and then inllating it so that it bears against the perforated body; gravel and bonding agent are then poured around the outside of the body, the bonding agent sets, and the inflatable body is deated.

Field of the invention The present invention relates to a method for making gravel filter pipes.

Description of the prior art Gravel filter pipes comprise a supporting internal tubular body provided with openings such as holes or slits and a layer of bonded gravel situated externally thereon. These pipes are made by placing an outer form around the tubular supporting body, pouring an aqueous mixture of gravel and bonding agent into the gap between form and body, then vibrating the mixture and finally allowing the mixture to set. v

It is necesasry in this manufacture to close temporarily the openings in the internal tubular body, so that the unset gravel mixture does not leak through them. Closure of these openings has heretofore been beset with difliculties. Most often sheet metal has been employed in the prior art for this purpose. The sheet metal is cylindrically curved and put into the interior of the supporting body. The sheets are braced, for example by wedges. In spite of carefully bracing of the sheets, it happens again and again that some individual wedges loosen when the mixture consisting of gravel and a bonding agent is vibrated. The mixture leaks through the openings in the supporting body into the pipe interior. In the case of long pipes with a comparatively big diameter this happens also owing to the fact that the sheets bend towards the interior and, therefore, at some points do not lie close to the openings. As a result, during the manufacturing process the sheet metal often sticks to the supporting body and can only be taken out with difficulty, in which case the sheets sometimes are so damaged that they are either entirely unfit for further -use or can only be m-ade reusable by toilsome manual labor.

Objects of the invention In view of the above diiculties, objects of the present invention are to provide a method for manufacturing gravel filter pipes wherein:

the openings of an inner tubular body are sealed during pouring and setting of a gravel and bonding agent mixture;

the sealing of an inner tubular body is unaffected by vibration of a poured mixture;

the seal is easily placed into the tubular body before pouring;

3,467,740 Patented Sept. 16, 1969 the seal is easily removed following setting of the mixture; the seal is not damaged during use and can be reused.

Description of the drawing The only gure of the drawing is a partly sectioned view of a llter pipe being manufactured according to the method of the invention.

Summary of the invention In order to attain the objects of the invention, the method of the invention involves putting an elastic, hollow, inflatable body into the interior of a perforated, tubular supporting body and inilating it therein. Because the interior limits of the gravel iilter pipe are formed by the supporting body, a comparatively thin-walled hollow body is suicient for sealing the openings of the supporting body. Such a hollow body, therefore, is very light and does not require much elastic material.

Because the hollow body to be used according to the invention need not be relatively thick and dimensionally stable, it adapts during iniation completely to all existing local unevennesses of the supporting body and reliably seals its openings, even if the inner surface of the supporting body is not entirely cylindrical.

According to the invention, a rubber, inilatable hollow body, made for example of latex and having a diameter corresponding to that of the perforated support body to be used for the pipe, is let into the interior of the support body. Then, the hollow body is inflated via a valve until it bears tightly against the inside of the support body and seals its openings. Then a mixture of gravel and bonding agent is poured into the hollow space between the support body and an outer form. The mixture is next vibrated to assure its uniform placement. After the mixture has set, the inating air is allowed to escape from the hollow body, whereupon the hollow body is withdrawn without diiculty and is ready for reuse.

The inflatable hollow body must be inflated to a pressure that will at least be greater than the static pressure of the gravel and bonding agent mixture surrounding the support body. It is also, of course, necessary that the pressure in the hollow body be sulcient to withstand the dynamic pressures arising from any vibrations used to obtain uniform placement of the mixture.

Description of the preferred embodiments The figure shows outer cylindrical forms 1 having vertical reinforcing elements 5. These forms 1 are held, in this example by their weight, to annular angle support rings 2 which are part of the tubular support bodies 6. The tubular support bodies have openings 3 in the form of slits or holes.

An iniated hollow body 4 is shown within the tubular support bodies. The hollow body is made of two sections and lapped at 7. Inflation of the hollow body is via an air valve 8.

A mixture of gravel and bonding agent is fed around the support body through the gaps 9.

I claim:

1. A method for placing a bonded gravel layer on a perforated support body to make gravel filter pipes, comprising, in sequence, the steps of: placing an inflatable body Within a perforated support body and placing a form around the outside of the support body; inating the inflatable body to bring it to bear with a predetermined pressure on the perforated internal surfaces of the support body; pouring a mixture of gravel and bonding agent around the outside of the support body; allowing the gravel and bonding agent mixture to set; and deating the inatable body.

2. A method as claimed in claim 1, further comprising the step of vibrating the mixture of gravel and bonding agent after the step of pouring before the step of setting.

3. A method as claimed in claim 1, further comprising 4 the step of removing the form from around the outside of the support body after the mixture has set.

4. A method as claimed in claim 1, further comprising the step of removing the iniiatable body from within the perforated support body, after the step of deating.

References Cited UNITED STATES PATENTS 2,585,756 2/1952 Eschenbrenner 264-87 2,311,358 2/1943 Baily 264-69 ROBERT F. WHITE, Primary Examiner R. SHEAR, Assistant Examiner U.S. Cl. X.R. 

